A. Field of the Invention
This invention relates generally to methods for communicating data over a data network, and, more particularly, to a method that allows signaling data to be communicated over the data network.
B. Description of the Related Art
Common Channel Signaling (CCS) provides a dedicated supervisory network for segregating signaling information from voice and data information in a telecommunications network. CCS was developed to meet the increased demands placed on the public telecommunications network by the growing market for voice, data, and information services. Previous signaling systems sent call setup and routing information over the same trunk circuit used for voice transmission. With CCS, a single out-of-band channel conveys signaling information relating to call setup, routing, and network management, among other things. Signaling System No. 7 (SS7), an international protocol standard for CCS communications, creates a standard format for communicating signaling information in a CCS network (CCS7).
FIG. 1 diagrammatically illustrates a PSTN having a CCS7 network 110 and a voice network 130, each of which interfaces with a plurality of service switching points (SSPs) 120. SSPs 120 are located at a central office to provide CCS7 trunk signaling and the capability to query a database to determine call routing. CCS7 network 110 includes STPs 112 which route CCS7 messages between SSPs and STPs and control access to the CCS7 network. In addition, each SSP 120 is connected to voice network 130, such as a long-distance telephone network by voice trunks 132.
The emergence of desktop computing, local area networks (LANs), and the Internet, brought the desire to carry CCS7 signaling data over data networks. Significant cost savings to communications providers could be realized if the CCS7 signaling data could be reliably transmitted over the existing data networks. The savings would stem from not having to install and maintain separate Signaling Networks; which are known to be extremely expensive in a telephone network, due largely in part to the inherent complexity required to achieve the high degree of reliability.
Any approach using a data network to carry CCS7 signaling data must also consider the reliability of the message transfer. In today""s data communication networks, reliable messaging of signaling data is generally performed by either: 1) utilizing a rigorous protocol implementation which corrects for lost messages; or 2) using fully duplicated transmission paths to minimize the impact of a break in one of the two transmission paths. In the most sensitive applications, such as in today""s telephone CCS7 Signaling Networks, these methods are combined to obtain maximum reliability of message transfer. This approach has a number of drawbacks. First, providing a duplicated and segregated data network just for the signaling data is expensive. Second, the number of specialized CCS7 signaling data routers (i.e., the STPs) increases the expense and the complexity of the system as well.
Within the computer industry, a different communication network has emerged based on Local and Wide Area Networks (LANs and WANs). These networks achieve reliability not by duplicated physical communication paths, but by the network""s ability to send messages based solely on a destination address and to have them arrive at the intended destination through a number of diverse routes. However, the network itself does not typically provide for guaranteed delivery of a particular message at the intended destination. The end points involved in a message exchange must, therefore, implement a rigorous protocol to detect lost messages and retransmit the detected lost messages. This is usually very processor and memory intensive, and the recovery of lost messages through retransmission is often slow-particularly when the network is geographically diverse, such as the Internet.
Some data communication networks today can support limited voice communications across a data network. FIG. 2 illustrates a data network 210, such as the Internet, connected to two telephony equipped personal computers (PC) 212 and 214. However, since data network 210 does not interface with a PSTN in this system, any communication of signaling data would be minimal and merely related to routing.
FIG. 3 illustrates a more advanced data network based system which supports voice communications. In FIG. 3, a telephone call connection path is formed for connecting a data network 310 to a PSTN 320 through a telephone gateway 350. A user of PC 312 on data network 310 may initiate a call by dialing the directory number (DN) of a telephone 322 on PSTN 320. PC 312 sends the DN in a message over data network 310 to a translation server 314, which uses the DN to determine the Internet protocol (IP) address of a gateway 350 closest to phone 322. Translation server 314 returns the IP address of gateway 350 to PC 312, which then sends the DN over data network 310 to phone gateway 350.
The system of FIG. 3, however, does not allow any signaling information (i.e., the calling party""s name and number) to be delivered between a data network 310 and PSTN 320. In addition, since telephone 322 cannot originate and complete a call to a PC 312, businesses would still require a traditional phone to receive calls from clients and customers. xe2x80x981-900xe2x80x99 calls dialed by PC 312 would be problematic since PSTN 320 would view telephone gateway 350 as the originator of the call and not PC 312. This occurs since phone gateway 350 effectively looks like a telephone to PSTN 320 since it is connected to PSTN 320 by a link terminating on a line circuit at an end office switch of PSTN 320. Thus, this system is unable to communicate the full complement of signaling information between a data network and a PSTN, prohibiting data network users from taking full advantage PSTN services.
Therefore, the above communication systems are not able to reliably and cost effectively transmit the full complement of signaling information regarding a call between a data network and a PSTN. This poses a serious barrier to the merging or integration of computer based telephony and the traditional telephone network PSTN.
Systems and methods consistent with the present invention provide a universal, high speed, highly reliable gateway for enabling voice and signaling communication between a data network and a PSTN.
To achieve these and other advantages, a method of communicating telephonic data regarding a call over a data network, comprising the steps of: receiving data units from a first data network over redundant communication paths; determining whether the received data units have an error; selecting one of the received data units from one of the redundant communication paths determined not to have an error; and forwarding the selected data unit to a second data network.
Both the foregoing general description and the following Detailed Description are exemplary and are intended to provide further explanation of the invention as claimed.